The them of this competitive renewal is unchanged: Understanding the biology of human hematopoietic stem cell (HSC) and their progeny will lead to improved stem cell transplantation therapy for a variety of methal malignant and non-malignant diseases. In Project 1, Dr. Catherine Verfaillie will perform in vitro and xenogeneic transplant experiments to determine how apoptosis, differentiation and proliferation affect symmetrical self-renewal of HSC. She will use this information to develop clinically relevant methods for HSC expansion and gene transfer applicable to clinical trials proposed in Projects 2 and 3. In Project 2, Dr. John Wagner will investigate engraftment of ex vivo expanded umbilical cord blood (UCB) HSC in a xenogeneic transplant model. He will conduct human transplantation trials using a single UCB graft containing a subpopulation of ex vivo expanded and genetically marked UCB. Alternatively, transplants will be performed with two HLA-identical UCB grafts-one expanded and genetically marked UCB. Alternatively, transplants will be performed with two HLA-identical UCB grants-one expanded ex vivo and one unmanipulated These studies will determine if ex vivo expansion of HSC has been achieved and what effects ex vivo expansion have on homing and engraft of HSC to the marrow.. In Project 3, Dr. Daniel Weisdorf will examine how mobilization regimen, cell source (marrow or blood) and phenotype (CD34+ or CD34-) influence HSC capacity for expansion, gene transfer and transplantation. These studies will be performed in vitro, in mouse and sheep xenogeneic transplant models and in clinical trials of autologous transplant therapy for lymphoma. Human clinical transplant trials performed in PROJECTS 2 and 3 will also validate the use of surrogate in vitro and in vivo HSC assays. In Project 4, Dr. Jeffrey Miller will investigate the contribution of BCR/ABL-mediated defective natural killer based immune surveillance and therapy in chronic myelogenous leukemia (CML). He will then test our immunotherapy with normal, allogeneic NK cells following autologous HSC transplant therapy for CM;. Finally, our group has demonstrate that marrow stromal cells can be derived in vitro from a mesodermal progenitor cell (MPC), and that in Hurler syndrome MPC- derived stromal cells contain abnormal heparan sulfate (HS) which inhibits normal HSC growth. In Project 5, Dr. Charles Peters and his co- investigators will explore the role of abnormal HS in Hurler stroma on defective hematopoietic support. He will also perform clinical trials in which normal, allogeneic MPC are transplanted in combination with hematopoietic cells (MPC/HCT) in order to "cross/correct" Hurler stromal defects and improve HSC engraftment and clinical outcome. These projects are supported by administrative and biostatistical cores, as well as cores to provide cell collection and processing NOD/SCID and other mouse assays and production of vectors suitable of clinical gene transfer.